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<title>Priority Queue Text Modify (Down) Timing Test</title>
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<h1>Priority Queue Text <tt>modify</tt> Timing Test - II</h1>
<h2><a name="description" id="description">Description</a></h2>
<p>This test inserts a number of values with keys from an
    arbitrary text ([ <a href="references.html#wickland96thirty">wickland96thirty</a> ]) into
    into a container then modifies each one "down" (<i>i.e.,</i> it
    makes it smaller). It uses <tt>modify</tt> for <tt>pb_ds</tt>'s
    priority queues; for the STL's priority queues, it pops values
    from a container until it reaches the value that should be
    modified, then pushes values back in. It measures the average
    time for <tt>modify</tt> as a function of the number of
    values.</p>
<p>(The test was executed with <a href="../../../../testsuite/performance/ext/pb_ds/priority_queue_text_modify_timing.cc"><tt>priority_queue_text_modify_down_timing_test</tt></a>
    thirty_years_among_the_dead_preproc.txt 200 200 2100 f)</p>
<h2><a name="purpose" id="purpose">Purpose</a></h2>
<p>The main purpose of this test is to contrast <a href="priority_queue_text_modify_up_timing_test.html">Priority Queue
    Text <tt>modify</tt> Timing Test - I</a>.</p>
<h2><a name="results" id="results">Results</a></h2>
<p>Figures <a href="#NPG">NPG</a>, <a href="#NPM">NPM</a>, and
    <a href="#NPL">NPL</a> show the results for the native priority
    queues and <tt>pb_ds</tt> 's priority queues in <a href="pq_performance_tests.html#gcc"><u>g++</u></a>, <a href="pq_performance_tests.html#msvc"><u>msvc++</u></a>, and
    <a href="pq_performance_tests.html#local"><u>local</u></a>,
    respectively; Figures <a href="#NRTG">NRTG</a>, <a href="#NRTM">NRTM</a>, and <a href="#NRTL">NRTL</a> show the results
    for the pairing heap and thin heaps in <a href="pq_performance_tests.html#gcc"><u>g++</u></a>, <a href="pq_performance_tests.html#msvc"><u>msvc++</u></a>, and
    <a href="pq_performance_tests.html#local"><u>local</u></a>,
    respectively,</p>
<div id="NPG_res_div">
<div id="NPG_gcc">
<div id="NPG_priority_queue_text_modify_down_timing_test">
<div id="NPG_pq">
<div id="NPG_Native_and__tt_pb_ds_455tt__priority_queue__tt_modify_455tt__timing_test"><div style="border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NPG" id="NPG"><img src="priority_queue_text_modify_down_timing_test_gcc.png" alt="no image" /></a></h6>NPG: Native and <tt>pb ds</tt> priority queue <tt>modify</tt> timing test - <a href="pq_performance_tests.html#gcc">g++</a><p>In the above figure, the names in the legends have the following meaning:</p>
<ol>
<li>
n_pq_deque-
<tt>std::priority_queue</tt> adapting <tt>std::deque</tt></li>
<li>
n_pq_vector-
<tt>std::priority_queue</tt> adapting <tt>std::vector</tt></li>
<li>
binary_heap-
<a href="priority_queue.html"><tt>priority_queue</tt></a>
 with <tt>Tag</tt> = <a href="binary_heap_tag.html"><tt>binary_heap_tag</tt></a>
</li>
<li>
thin_heap-
<a href="priority_queue.html"><tt>priority_queue</tt></a>
 with <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a>
</li>
<li>
rc_binomial_heap-
<a href="priority_queue.html"><tt>priority_queue</tt></a>
 with <tt>Tag</tt> = <a href="rc_binomial_heap_tag.html"><tt>rc_binomial_heap_tag</tt></a>
</li>
<li>
binomial_heap-
<a href="priority_queue.html"><tt>priority_queue</tt></a>
 with <tt>Tag</tt> = <a href="binomial_heap_tag.html"><tt>binomial_heap_tag</tt></a>
</li>
<li>
pairing_heap-
<a href="priority_queue.html"><tt>priority_queue</tt></a>
 with <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a>
</li>
</ol>
</div><div style="width: 100%; height: 20px"></div></div>
</div>
</div>
</div>
</div>
<div id="NPM_res_div">
<div id="NPM_msvc">
<div id="NPM_priority_queue_text_modify_down_timing_test">
<div id="NPM_pq">
<div id="NPM_Native_and__tt_pb_ds_455tt__priority_queue__tt_modify_455tt__timing_test"><div style="border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NPM" id="NPM"><img src="priority_queue_text_modify_down_timing_test_msvc.png" alt="no image" /></a></h6>NPM: Native and <tt>pb ds</tt> priority queue <tt>modify</tt> timing test - <a href="pq_performance_tests.html#msvc">msvc++</a><p>In the above figure, the names in the legends have the following meaning:</p>
<ol>
<li>
n_pq_deque-
<tt>std::priority_queue</tt> adapting <tt>std::deque</tt></li>
<li>
n_pq_vector-
<tt>std::priority_queue</tt> adapting <tt>std::vector</tt></li>
<li>
binary_heap-
<a href="priority_queue.html"><tt>priority_queue</tt></a>
 with <tt>Tag</tt> = <a href="binary_heap_tag.html"><tt>binary_heap_tag</tt></a>
</li>
<li>
thin_heap-
<a href="priority_queue.html"><tt>priority_queue</tt></a>
 with <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a>
</li>
<li>
rc_binomial_heap-
<a href="priority_queue.html"><tt>priority_queue</tt></a>
 with <tt>Tag</tt> = <a href="rc_binomial_heap_tag.html"><tt>rc_binomial_heap_tag</tt></a>
</li>
<li>
binomial_heap-
<a href="priority_queue.html"><tt>priority_queue</tt></a>
 with <tt>Tag</tt> = <a href="binomial_heap_tag.html"><tt>binomial_heap_tag</tt></a>
</li>
<li>
pairing_heap-
<a href="priority_queue.html"><tt>priority_queue</tt></a>
 with <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a>
</li>
</ol>
</div><div style="width: 100%; height: 20px"></div></div>
</div>
</div>
</div>
</div>
<div id="NPL_res_div">
<div id="NPL_local">
<div id="NPL_priority_queue_text_modify_down_timing_test">
<div id="NPL_pq">
<div id="NPL_Native_and__tt_pb_ds_455tt__priority_queue__tt_modify_455tt__timing_test"><div style = "border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NPL" id= "NPL"><img src="priority_queue_text_modify_down_timing_test_local.png" alt="no image" /></a></h6>NPL: Native and <tt>pb ds</tt> priority queue <tt>modify</tt> timing test - <a href = "pq_performance_tests.html#local">local</a></div><div style = "width: 100%; height: 20px"></div></div>
</div>
</div>
</div>
</div>
<div id="NRTG_res_div">
<div id="NRTG_gcc">
<div id="NRTG_priority_queue_text_modify_down_timing_test_pairing_thin">
<div id="NRTG_pq">
<div id="NRTG_Pairing_and_thin__priority_queue__tt_modify_455tt__timing_test"><div style="border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NRTG" id="NRTG"><img src="priority_queue_text_modify_down_timing_test_pairing_thin_gcc.png" alt="no image" /></a></h6>NRTG: Pairing and thin  priority queue <tt>modify</tt> timing test - <a href="pq_performance_tests.html#gcc">g++</a><p>In the above figure, the names in the legends have the following meaning:</p>
<ol>
<li>
thin_heap-
<a href="priority_queue.html"><tt>priority_queue</tt></a>
 with <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a>
</li>
<li>
pairing_heap-
<a href="priority_queue.html"><tt>priority_queue</tt></a>
 with <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a>
</li>
</ol>
</div><div style="width: 100%; height: 20px"></div></div>
</div>
</div>
</div>
</div>
<div id="NRTM_res_div">
<div id="NRTM_msvc">
<div id="NRTM_priority_queue_text_modify_down_timing_test_pairing_thin">
<div id="NRTM_pq">
<div id="NRTM_Pairing_and_thin__priority_queue__tt_modify_455tt__timing_test"><div style="border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NRTM" id="NRTM"><img src="priority_queue_text_modify_down_timing_test_pairing_thin_msvc.png" alt="no image" /></a></h6>NRTM: Pairing and thin  priority queue <tt>modify</tt> timing test - <a href="pq_performance_tests.html#msvc">msvc++</a><p>In the above figure, the names in the legends have the following meaning:</p>
<ol>
<li>
thin_heap-
<a href="priority_queue.html"><tt>priority_queue</tt></a>
 with <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a>
</li>
<li>
pairing_heap-
<a href="priority_queue.html"><tt>priority_queue</tt></a>
 with <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a>
</li>
</ol>
</div><div style="width: 100%; height: 20px"></div></div>
</div>
</div>
</div>
</div>
<div id="NRTL_res_div">
<div id="NRTL_local">
<div id="NRTL_priority_queue_text_modify_down_timing_test_pairing_thin">
<div id="NRTL_pq">
<div id="NRTL_Pairing_and_thin__priority_queue__tt_modify_455tt__timing_test"><div style = "border-style: dotted; border-width: 1px; border-color: lightgray"><h6 class="c1"><a name="NRTL" id= "NRTL"><img src="priority_queue_text_modify_down_timing_test_pairing_thin_local.png" alt="no image" /></a></h6>NRTL: Pairing and thin  priority queue <tt>modify</tt> timing test - <a href = "pq_performance_tests.html#local">local</a></div><div style = "width: 100%; height: 20px"></div></div>
</div>
</div>
</div>
</div>
<h2><a name="observations" id="observations">Observations</a></h2>
<p>Most points in these results are similar to <a href="priority_queue_text_modify_up_timing_test.html">Priority Queue
    Text <tt>modify</tt> Timing Test - I</a>.</p>
<p>It is interesting to note, however, that as opposed to that
    test, a thin heap (<a href="priority_queue.html"><tt>priority_queue</tt></a> with
    <tt>Tag</tt> = <a href="thin_heap_tag.html"><tt>thin_heap_tag</tt></a>) is
    outperformed by a pairing heap (<a href="priority_queue.html"><tt>priority_queue</tt></a> with
    <tt>Tag</tt> = <a href="pairing_heap_tag.html"><tt>pairing_heap_tag</tt></a>).
    In this case, both heaps essentially perform an <tt>erase</tt>
    operation followed by a <tt>push</tt> operation. As the other
    tests show, a pairing heap is usually far more efficient than a
    thin heap, so this is not surprising.</p>
<p>Most algorithms that involve priority queues increase values
    (in the sense of the priority queue's comparison functor), and
    so <a href="priority_queue_text_modify_up_timing_test.html">Priority Queue
    Text <tt>modify</tt> Timing Test - I</a> is more interesting
    than this test.</p>
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